AC-DC power converter

1. An AC-DC power converter, comprising: a) a front-stage power circuit; b) a rear-stage power circuit configured to share one power switch as a main power switch with the front-stage power circuit, wherein the rear-stage power circuit is coupled to a load, and a first magnetic component of the front-stage power circuit and a second magnetic component of the rear-stage power circuit are not coupled in one conductive loop from a positive terminal of a DC input voltage to a negative terminal of the DC input voltage; and c) an energy storage capacitor coupled to the front-stage power circuit and the rear-stage power circuit, wherein a common node of the first and second magnetic components is directly connected to the power switch with no other components therebetween.

2. The AC-DC power converter of claim 1 , wherein when the DC input voltage is greater than a voltage on the energy storage capacitor, at least part of energy provided by the DC input voltage is directly transferred to the load through one power conversion of the rear-stage power circuit in each switching period.

3. The AC-DC power converter of claim 1 , wherein when the power switch is turned on, the first magnetic component stores energy provided by the DC input voltage, and simultaneously the second magnetic component stores energy provided by at least one of the DC input voltage and the energy storage capacitor.

4. The AC-DC power converter of claim 2 , wherein the energy storage capacitor is charged by the front-stage power circuit, and when the DC input voltage is less than the voltage on the energy storage capacitor, the rear-stage power circuit supplies energy to the load at least by the energy discharged by the energy storage capacitor.

5. The AC-DC power converter of claim 2 , wherein when the DC input voltage is greater than the voltage on the energy storage capacitor, the DC input voltage supplies power to the front-stage power circuit and the rear-stage power circuit.

6. The AC-DC power converter of claim 4 , wherein when the DC input voltage is less than the voltage on the energy storage capacitor, the energy storage capacitor supplies power to the rear-stage power circuit, and the front-stage power circuit does not operate or the DC input voltage supplies power to the front-stage power circuit.

7. The AC-DC power converter of claim 6 , wherein the AC-DC power circuit comprises a first diode, wherein an anode of the first diode is coupled to a positive electrode of the energy storage capacitor, a cathode of the first diode is coupled to a first output terminal of the DC input voltage and the power switch.

8. The AC-DC power converter of claim 7 , wherein the front-stage power circuit comprises: a) the first magnetic component having one terminal coupled to a first terminal of the power switch, and the other terminal coupled to an anode of a second diode; and b) the second diode having a cathode coupled to the positive electrode of the energy storage capacitor.

9. The AC-DC power converter of claim 8 , wherein the rear-stage power circuit comprises: a) a first transformer having a primary winding and a secondary winding, wherein a first terminal of the primary winding is coupled to a common node of the power switch and the first magnetic component; b) a third diode having an anode coupled to the secondary winding of the first transformer; c) a fourth diode having a cathode coupled to a cathode of the third diode, and an anode coupled to a reference ground of the secondary winding; and d) a second inductor having one terminal coupled to the cathode of the fourth diode, and the other terminal coupled to the load, wherein the power switch, the first transformer, the third diode, the fourth diode, and the second inductor form a forward circuit.

10. The AC-DC power converter of claim 8 , wherein the rear-stage power circuit further comprises: a) a second magnetic component having a first terminal coupled to a common node of the power switch and the first magnetic component, and a second terminal coupled to a ground; and b) a fifth diode having a cathode coupled to a common node of the second magnetic component and the power switch.

11. The AC-DC power converter of claim 6 , wherein the front-stage power circuit comprises the first magnetic component, forming a first loop with the power switch and the DC input voltage, wherein the first magnetic component stores energy provided by the DC input voltage through the first loop.

12. The AC-DC power converter of claim 11 , wherein the front-stage power circuit further comprises a sixth diode having a cathode coupled to a positive electrode of the energy storage capacitor, and an anode coupled to a ground, wherein the sixth diode is configured to provide a freewheeling loop for the first inductive inductor.

13. The AC-DC power converter of claim 12 , wherein the rear-stage power circuit comprises a seventh diode and the second magnetic component, wherein a cathode of the seventh diode is coupled to the ground and an anode of the seventh diode is coupled to the second magnetic component through the load, and the seventh diode is configured to provide a freewheeling loop for the second magnetic component.

14. The AC-DC power converter of claim 13 , wherein the rear-stage power circuit further comprises an eighth diode having an anode coupled to the positive electrode of the energy storage capacitor, and a cathode coupled to the power switch, wherein the eighth diode is configured to provide a loop for the second magnetic component to store energy provided by the energy storage capacitor, when the DC input voltage is less than the voltage on the energy storage capacitor.